Persistent contaminants may be present in very low environmental concentrations and yet exert considerable effects on living organisms through the phenomenon of bioaccumulation. Current sample collection, preparation, and analysis practices in environmental engineering that characterize the bioavailability of such compounds may underestimate or overestimate the actual concentrations affecting aquatic or sedimentary biota exposed to such compounds.
Contamination of U.S. surface water sediments is a daunting problem requiring novel solutions for monitoring and remediation. According to the U.S. Environmental Protection Agency (EPA), some 1.2 billion cubic yards of U.S. surficial water sediments (i.e., as found in the top 5 cm of the water surface) are contaminated with toxic pollutants to a degree that poses potential risks to fish as well as to fish-consuming wildlife and humans. Whereas the presence of contaminants in sediments warrants investigation to protect ecosystems and public health, it has long been appreciated that sediment pollution does not necessarily pose a risk that is directly proportional to the mass of contaminants present. Instead, the bioavailability of the pollutants is key information that needs to be known to inform risk assessments for potential human health impacts.
The need for bioavailability data has triggered a renewed interest in the development of novel sampling strategies for the determination of truly dissolved contaminant mass in both bulk water and pore water. Due to partitioning and sorption of contaminants to sediment constituents, including organic carbon, black carbon and soot, the bioavailable contaminant mass of organic pollutants in the dissolved or easily desorbable state typically is only a small fraction of the total mass of the respective contaminant in sediment (typically determined via extraction at high temperature and/or pressure with aggressive organic solvents).
A number of passive sampling strategies have been introduced to enable convenient and inexpensive determination of contaminant concentrations in sediment pore water and bulk water of polluted aquatic environments. While these systems represent a significant advance in environmental monitoring, they also have a number of limitations. Passive samplers which are based on polyethylene and similar sorbents typically capture only a limited spectrum of contaminants and may require performance reference compounds (PRCs) to produce reliable results. Converting analyte mass on the sampler to units of concentration also can be challenging. They also are fragile and may be subject to biodegradation during in situ incubation.
As disclosed in the applications referenced above, FIGS. 1A and 1B provide a schematic of a prior art device in use. Environmental water enters the device 1 through the water intake zone 103. Water is collected in the optional multi-channel reservoir 105 concomitantly during the time period of sampling if desired, either short or long term. During sampling, the pump 107 is used to apply the sample to the non-aqueous collection matrix cartridges 111 at the appropriate flow rate and to deliver, a split sample to the optional reservoir 105 if desired. The separation process is demonstrated schematically. The reservoir includes spots of four different shades of gray. After passing through the pump and contacting the non-aqueous collection matrix columns 111, each of the columns has turned the same shade of gray as one of the spots, representing that each column binds a specific analyte. As in the previous figure, the water from the columns is discharged either above or below the sampling zone to prevent contamination of the sample. It is understood that some types of non-aqueous collection matrices can bind more than one analyte.
Still referring to the referenced patent applications, FIGS. 2A and 2B provide a schematic of an individual non-aqueous collection matrix column 111 that binds a single analyte. Prior to exposure to the sample, the non-aqueous collection matrix includes multiple empty analyte binding sites 301. After contacting the non-aqueous collection matrix with the sample 303, the analyte 305 that specifically binds the non-aqueous collection matrix is bound to the non-aqueous collection matrix in the column. The analytes or other components of the sample that do not bind the non-aqueous collection matrix 307, passes through the column without binding to the non-aqueous collection matrix.
Still referring to the referenced patent applications, FIGS. 3A and 3B show a prior art sampling device wherein a real time sensor 401 is attached to the non-aqueous collection matrix column 403 to allow for detection of the analyte 405 bound to the column. In the embodiment, the real time sensor is further connected for signal transmission, with wire 407 or wirelessly, to a data logger to record the presence of the analyte bound to the sensor. Data can be sent to the data logger at timed intervals, continuously, upon a certain event such as saturation of the column. In an embodiment, a real time sensor can be used to analyze the liquid and the constituents therein 409 that do not bind to the column. In one embodiment, the liquid and the constituents contained therein 409 also can be diverted to the reservoir 105 for a post-deployment determination of the collection efficiency of the non-aqueous collection matrix cartridges 111.
In environmental studies, it also is desirable to obtain a series of time-discrete samples to enable the calculation of rates, for example, of biotransformation and pollutant destruction. Currently, this requires the acquisition, storage and analysis of multiple fluid samples, analysis results of which can inform the rate determination calculations. Storage of large volumes of fluids can be problematic when space is limited or when the analytes of interest are labile and subject to ready disintegration. The present disclosure provides new and novel solutions to overcome the problems inherent in the art related to storing large volumes of unstable liquids. Here disclosed is a method that enables rate determination without requiring the storage and preservation of multiple fluid samples. Although the referenced patent applications disclose technology that has advanced the art, improvement is needed particularly for measurements carried out in aquatic and saturated sedimentary environments. The present disclosure provides new and novel solutions to overcome the limitations inherent in the art. These apparatuses and methods are suitable to make measurements of bioavailability of pollutants. As such, they enable a determination of whether a given environment is posing risks to humans and other biological species due to pollutants that have accumulated in sediments. This information is critically needed by regulatory agencies overseeing and consulting firms serving potentially responsible parties (PRPs) for environmental pollution.
Additionally, it is important to determine information on the kinetics of reactions and processes of interest to address the growing public concern about environmental contamination and its impact on health, agriculture, water supplies and other detrimental effects in the U.S. and around the world. As a result, it is becoming increasing important to demonstrate the effectiveness of environmental remediation processes, even long after a particular remediation site may have been shut down, for example. It is desirable that measurements provide accurate proof of long-term effects and not just discrete time samples (a.k.a. grab samples) or time-average samples, which may or may not be acceptable as reliable evidence of effectiveness in a legal setting, for example.